Yeah, this argument has been going on for years. Head on over the SVRider forum or the Little Monster forum where kids try to squeeze 180's where 160's should be. All in the name of lookin' cool. But I'll tell you what looks cool. Riding well while wearing top-shelf kit and tinted visor. Thats way cooler than a phat tire.
There is no real advantage to putting a 190 on a 5.5" rim. It is within specifications to do it and honestly, every tire manufacturer measures width a little bit differently, but...
If you do, you should put on a 190/50-17 and not a 190/55-17. The narrower rim will pinch the tire into the beads and cause the tire to be more pointy. The 190/55 is already a fair bit taller and pointier, then you pinch it into the 5.5" rim (when it's intended for a 6" rim) and you are raising the rear of the bike and making changes to the bikes geometry - so it will feel different. But the tire really wont' look much wider and you're not really getting much in the way of "more contact patch" because the tire flexes and deforms while riding anyway.
But, the 180 will be lighter and cheaper, and look just the same. If you want a tire to look really wide, run Dunlops - their 180 is physically wider than most people's 190.
Personally, I prefer the 5.5" wheel and the 180/55. It's a damned good combination IMHO and the few bucks I save on the difference goes into my track-day fund.
dp
